AURORA, Colo. (AP) -- Police and firefighters have started their attempt at entering the booby trapped apartment of the man suspected of gunning down dozens of people at a Colorado movie theater to remove trip wires, a process that might include a controlled detonation that causes a loud boom and possibly a fire.
Local agencies elicited the help of bomb experts in coming up with a plan to enter the apartment while keeping people safe and preserving evidence inside.
Officials positioned vehicles and personnel around the apartment building.
Authorities will alert people before any detonation and tell them what to expect, Aurora police Sgt. Cassidee Carlson told reporters Saturday morning.
The first goal is to make the area safe, then remove items from the apartment that could explode, including about 30 shells that will be placed in sand trucks and taken to a disposal site, she said.
There's no timeline.
"I can't put an end time on it," Carlson said. "We don't need to rush anything."
The suspect in the shooting, James Holmes, 24, lives in a third-floor unit of the building.
Police evacuated the building and surrounding residences after arresting him at a midnight screening of "The Dark Knight Rises." Twelve people were killed in the attack and about five dozen were injured, authorities said.
"It's a pretty extensive booby trap. We're not sure what it's attached to. There are trip wires. There are three containers and we don't know what's inside," said Chris Henderson, deputy Aurora fire chief.
Photos of Holmes' apartment appeared to show jars full of accelerant and other items unlike anything Aurora Police Chief Dan Oates had ever seen.
"I personally have never seen anything like what the pictures show us is in there," he said.
Friday evening police escorted residents individually and in pairs to their apartment units so they could quickly gather personal items.
Roberto Martinez, who lives in a building next to the suspect's building, hadn't been home since 4:30 a.m. Friday. He was escorted into his apartment and came out with a trash bag filled with items including toiletries, ice, a basketball and Air Jordan shoes.
He opted to stay in a hotel for the night instead of a shelter at a local high school, where some families with children were staying.
More than two dozen people were using a shelter at the Aurora Central High School Gymnasium.
Red Cross spokeswoman Melinda Epp said up to 30 residents were using the shelter to escape the heat, feed their children and wait out their exile. It was unclear how many people planned to spend the night there.
Kaitlyn Fonzi, 20, a graduate student at University Hospital, said she lives in the apartment below that of the suspect.
About midnight, Fonzi said she heard techno-like, deep-based reverberating music coming from that unit apartment. She went upstairs to the suspect's place and put her hand on the door handle. She felt it was unlocked, but she didn't know if he was there and decided not to confront him.
"I yelled out and told him I was going to call the cops and went back to my apartment," she said.
Fonzi called police, who told her they were busy with a shooting and did not have time to respond to a noise disturbance. She said she was surprised to learn later that the apartment was booby trapped and was shaken by the news.
"I'm concerned if I had opened the door, I would have set it off," she said.
Fonzi said she had seen the man one or two times before but never talked with him.
She said she believes the music was on a timer because it started about the time of the shootings.
Police have searched apartments and broken out windows at the building, but Fonzi said she doesn't know the condition of her apartment or car.
University of Colorado pharmacy student Ben Lung, 27, who lives two floors down from the suspect, said he and other residents were evacuated around 2 a.m. by armed SWAT officers armed with rifles.
"I heard a loud crash. It sounded like an air conditioner falling to the ground. About 10 minutes later, I heard police knock on my door. Police were armed with assault rifles and they brought us outside the apartment building and started questioning us," Lung said.
Lung said a few residents upstairs had called police around midnight and complained about loud music coming from the suspect's apartment.
Michelle Thuis, 26, who lives in an apartment near the entrance to the building, said police woke her up when they stormed in around 2:30 a.m.
"I heard them breaking down the front door. I called the police on them, then I looked out and saw it was the police," she said.
Thuis described the building as quiet and populated largely by students and doctors affiliated with a nearby University of Colorado Denver medical campus.